The presentation is here.
The A5/1 cracking project homepage is here.
GSM is used by many major cellular providers such as AT&T and T-Mobile (see GSM Coverage Map). The main alternative to GSM network is CDMA which is used by providers such as Verizon, Alltel and US Cellular (see CDMA World Map).
The ability to decrypt A5/1 encryption would enable an attacker to listen in to all cellular communications made over a GSM network. To execute the attack the attacker would need to be close enough to the target to monitor the radio waves emitted from the phone. However, this isn't much of a restriction since the radio waves can be picked up from quite some distance.
This attack should raise serious concerns about the sensitivity of information exchanged over cell phones. An attacker with this equipment situated near a major corporate office or within a large city could easily glean very sensitive data from cellular voice calls.
Regarding data exchanged over cellular phones (e.g.
A bit about the attack
The attack leverages rainbow tables for a Time-Memory Trade-Off based attack. The A5/1 cracking project is enabling volunteers to help develop the rainbow tables for the A5/1 cipher and distributing the generated tables over bittorrent. Clever adaptations were made to the rainbow table generation to minimize the number of tables that were needed and thus dramatically reduced the required processing efforts.